| Number | Name | Date | Kind |
|---|---|---|---|
| 3642778 | Helsley | Feb 1972 | |
| 3642779 | Helsley | Feb 1972 | |
| 3939159 | Dornauer | Feb 1976 |
| Entry |
|---|
| Carter et al., Journal of Heterocyclic Chemistry, vol. 24, pp. 387-391. |
| Duncan et al., Journal of Heterocyclic Chemistry, vol. 10, pp. 65-70, Feb. 1973. |
| Sugasawa et al., Journal of the American Chemical Society, vol., pp. 4842-4852 (1978). |